1. Field of the Invention
The invention relates to a method for determining the thickness of a layer of lacquer which is applied by electrophoretic immersion coating to an article, wherein the article for immersion coating is immersed in a lacquer immersion bath containing lacquer and generates an electrical field as an electrode with at least one counter electrode. The invention also relates to a system for determining the thickness of a layer of lacquer which is applied by electrophoretic immersion coating to an article, comprising an immersion bath for receiving a lacquer in which the article can be immersed, a voltage source, of which one pole can be connected to the article and of which the other pole is connected to at least one counter electrode reaching into the immersion bath.
The invention relates to a system and a method for determining the thickness of a layer of lacquer which is applied by electrophoretic immersion coating to an article.
2. Description of the Art
When lacquer coating articles it is generally important that the applied layer of lacquer has the predetermined desired thickness as precisely as possible. If the actual thickness differs excessively from the desired thickness then the quality of the lacquer coating, for example the durability or the colour effect, will usually be impaired. Excessively thickly applied layers of lacquer also lead to unnecessarily high lacquer consumption, and this should be avoided from cost and environmental perspectives.
In the case of electrophoretic lacquer coating of articles in immersion baths, it is not generally possible to ensure that the desired thickness of the layers of lacquer is maintained over a relatively long period merely by adhering to predetermined process conditions. Thus, for example, the properties of the lacquer may change over time. Contact of the article with the voltage source also frequently leads to difficulties. A loose connection in the region of the contacting area is directly reflected in a reduced layer thickness.
Previously, for quality control, the thickness of electrophoretically applied layers of lacquer has generally been determined manually, for example using a measuring microscope or a capacitive measuring device, after drying. If it is established during the course of this that the thickness of the applied layer of lacquer differs from the desired thickness beyond the tolerance limits, the faults responsible for this can be discovered and optionally eliminated. Re-coating is possible, however, in the case of excessively thin layers of lacquer, if need be after removing the dried layer of lacquer. As rejects the articles that are lacquer coated too thinly or thickly increase the production costs considerably.
For this reason it has already been proposed that the thickness of the layer of lacquer be determined directly after emergence from the lacquer immersion bath and not firstly after drying. As the lacquer has not yet cured at this point, re-coating is optionally possible by way of re-immersion in the lacquer immersion bath. The measuring devices required for this are very expensive however and lead to a loss of time and sometimes to a loss of quality if the wet lacquer coating is damaged.
The present invention is directed to resolving these and other matters.